homelist2: Generate an index of user homepages

22. letterInfo(): Information about a
subpage

# - - - l e t t e r I n f o
def letterInfo(dirPath, letter):
'''Find the URL, path, and title of the subpage for one letter.
[ (dirPath is a path relative to TCC_URL) and
(letter is a single unicode character) ->
return (URL of letter's page, absolute path to letter's
page, Unicode title of letter's page) ]
'''

Because the letter may be a non-ASCII Unicode
character, we can't use it directly in the name of the letter
page. Instead, for code points past a lowercase
“z”, we'll use a string of the form “uNNNN” where NNNN is the hexadecimal
value of the code point.